JP4659839B2 - Apparatus and method for signal encryption / decryption in communication system - Google Patents

Description

  The present invention relates to an apparatus and method for ciphering / deciphering a signal in a communication system.

  In next-generation communication systems, active research is being conducted to provide users with services having various service qualities (“QoS”) at high transmission rates.

  Wireless short-distance communication network (Local Area Network: hereinafter referred to as “LAN”) communication systems and wireless urban area network (Metropolitan Area Network: hereinafter referred to as “MAN”) communication systems support high transmission rates. Here, the wireless MAN communication system is a broadband wireless access (hereinafter referred to as “BWA”) communication system, which has a wider service area than the wireless LAN communication system and supports a higher transmission rate. . In the next generation communication system, it is possible to guarantee the mobility and QoS of a subscriber station (hereinafter referred to as “SS”) in a wireless LAN and MAN communication system that guarantee a relatively high transmission rate. Research that can develop new communication systems capable of supporting high-speed services provided by next-generation communication systems is actively underway.

  Orthogonal Frequency Division Multiplexing (hereinafter referred to as “OFDM”) and Orthogonal Frequency Division Multiplexing (Orthogonal) to support a broadband transmission network in a physical channel of a wireless MAN communication system A system to which the Frequency Division Multiple Access (hereinafter referred to as “OFDMA”) system is applied is based on the IEEE (Institute of Electrical and Electronics Engineers) 802.16 standard. This system is referred to as an “IEEE802.16 communication system”. Called. Since the IEEE 802.16 communication system applies the OFDM / OFDMA scheme in a wireless MAN communication system, high-speed data transmission is possible by transmitting physical channel signals through a plurality of subcarriers. Hereinafter, for the convenience of description, the IEEE 802.16 communication system will be described as an example of a BWA communication system.

  As described above, in order to provide high-speed data transmission in the IEEE 802.16 communication system, a multicast and broadcast service (Multicast that can provide the same service to a plurality of SSs while minimizing resource usage, in particular. and Broadcast Service (hereinafter referred to as “MBS”). What service providers consider most in MBS are user authentication and billing issues. Therefore, in order to perform user authentication and accounting for the SS that receives MBS data, it is necessary to accurately detect when the SS starts to receive MBS data and when it stops receiving MBS data. For this purpose, a transmitter that transmits MBS data, for example, a base station (BS), encrypts MBS data that can be received only by a receiver who can charge a service fee, for example, SS. When receiving MBS data, the SS must decrypt the encrypted MBS data.

  In order to decrypt the MBS data encrypted by the BS, the BS must send information for the decryption to the SS.

  Here, referring to FIG. 1 and FIG. 2, encryption in AES (Advanced Encryption Standard) -CTR (Counter Mode Encryption) mode for defining encryption and decryption methods used in the IEEE 802.16 communication system / Describe the decoding operation.

FIG. 1 shows an MBS payload format used in a general IEEE 802.16 communication system.
Referring to FIG. 1, the MBS payload includes a generic medium access control (hereinafter referred to as “MAC”) header field (Generic MAC header: hereinafter referred to as “GMH”) field 111, a NANCE field 113, and An MBS stream field 115 and a CRC (Cyclic Redundancy Check) field 117 are included.

  The GMH header field 111 includes a GMH header that is a MAC header having a predetermined length. The NANCE field 113 includes a nonce used to generate an initial counter value of the counter in the AES-CTR mode. The MBS stream field 115 includes an MBS stream. The CRC field 117 includes a CRC value for confirming the occurrence of an error in the MBS payload. The MBS stream included in the MBS stream field 115 is generated from the encrypted MBS data. The nonce size preferably has the same size as the MBS data before encryption. However, the nonce size is not necessarily the same as the size of the MBS data before encryption. In the IEEE 802.16 communication system, the nonce size is set to 32 bits.

FIG. 2 is a block diagram showing the structure of an AES-CTR encryption apparatus used in the AES-CTR mode of a general IEEE 802.16 communication system.
Referring to FIG. 2, the AES-CTR encryption apparatus includes an AES-CTR encryptor 200 and an initial counter value generator 211. The AES-CTR encryptor 200 includes a counter 213, n cipher block generators, that is, first to n-th cipher block generators 215-1 to 215-n, and n exclusive ORs ( exclusive OR: hereinafter referred to as “XOR”), that is, first to nth XOR operators 217-1 to 217-n.

  When MBS data to be transmitted is generated, the MBS data to be transmitted, the nonce, and the MBS traffic key (hereinafter referred to as “MTK”) are input to the AES-CTR encryptor 200. Here, the MBS data is fragmented into n plain texts, that is, first to nth plain texts. Each of the n plain texts is input to the corresponding XOR operator. That is, the first plain text is input to the first XOR operator 217-1, and similarly, the nth plain text is input to the nth XOR operator 217-n. Nonce is currently set to a 32-bit random number in the IEEE 802.16 communication system. This 32-bit nonce is input to the initial counter value generator 211. The MTK is input to the first to nth cipher block generators 215-1 to 215-n.

  The initial counter value generator 211 receives the nonce and generates a 128-bit initial counter value by repeating a predetermined number of times, for example, four times. Then, the initial counter value generator 211 outputs the generated initial counter value to the counter 213. The counter 213 receives the initial counter value from the initial counter value generator 211 and increases n by 1 to generate n counter values. The counter 213 outputs each of the n counter values to the corresponding cipher block generator. That is, the counter 213 outputs the first counter value generated by incrementing the initial counter value by 1 to the first cipher block generator 215-1. The counter 213 outputs the second counter value generated by incrementing the initial counter value by 2 to the second cipher block generator 215-2. Thus, the counter 213 outputs the nth counter value generated by increasing the initial counter value by n to the nth cipher block generator 215-n.

  Each of the n cipher block generators receives the MTK and the counter value output from the counter 213, generates a cipher block, and outputs the cipher block to the corresponding XOR operator. That is, the first cipher block generator 215-1 generates the first cipher block using the first counter value output from the counter 213 and the MTK, and then the first XOR operator 217-1. This cipher block is output to In this way, the n-th cipher block generator 215-n generates the n-th cipher block using the n-th counter value output from the counter 213 and the MTK, and the n-th XOR operator 217-n. This cipher block is output to

  Each of the n XOR operators receives the encryption block output from the corresponding encryption block generator and the corresponding plain text, performs an XOR operation, and outputs an MBS stream. That is, the first XOR operator 217-1 receives the first cipher block and the first plain text output from the first cipher block generator 215-1, and performs the XOR operation. An MBS stream is generated and output. As described above, the nth XOR operator 217-n receives the nth cipher block and the nth plain text output from the nth cipher block generator 215-n, and performs an XOR operation. An nth MBS stream is generated and output.

  As described above, since the AES-CTR encryptor uses the same MTK, more stable encryption uses the same MTK and sets the initial counter value of the counter during the time interval. It can be accomplished by changing. Since the current IEEE 802.16 communication system generates nonce in the form of a random number, the initial counter value used before the previous time interval, that is, the MTK refresh may be reused in the next time interval. There is. In this case, the stability of the encryption operation is not guaranteed. It is very important to avoid repeated initial counter values or collisions between initial counter values. Since there is a risk of hacking when the initial counter value is the same in the time interval using the same MTK, the initial counter value should not be repeated in the time interval using the same MTK. Don't be.

  Minimizing the amount of data that must be transmitted for encryption and decryption as well as encryption stability is very important when considering the overall performance of the system. However, in the current IEEE 802.16 communication system, a 32-bit nonce must be transmitted for each MBS stream in order to transmit an MBS stream, so that the data transmission capacity is reduced by this nonce.

Accordingly, an object of the present invention is to provide a signal encryption / decryption apparatus and method in a communication system.
It is another object of the present invention to provide a signal encryption / decryption apparatus and method capable of avoiding a collision between initial counter values in an AES (Advanced Encryption Standard) -CTR (Counter mode) mode in a communication system. It is in.
It is another object of the present invention to provide a signal encryption / decryption apparatus and method capable of minimizing additional data transmission in an AES-CTR mode in a communication system.

  In order to achieve the above object, the present invention is a signal transmission apparatus in a communication system, and generates second encrypted information using the first encrypted information. An encryption device that encrypts the data using the second encryption information and the third encryption information when data to be transmitted is generated, the encrypted data, and the first data And a signal generator for generating and transmitting a signal including the encrypted information.

  The present invention is also an apparatus for transmitting an MBS (Multicast and Broadcast Service) stream in a communication system, and generates an initial counter value using a frame number and a rollover counter (ROC) of the communication system. A generator, a counter for generating n counter values by incrementing the initial counter value by 1 when MBS data to be transmitted is generated, and the n counter values and an MBS traffic key (MTK). Using the n cipher block generators to generate n cipher blocks, an exclusive OR (XOR) operation is performed on the cipher blocks and the n plain texts generated by fragmenting the MBS data. And n XOR operators for generating MBS streams.

  The present invention includes a step of generating second encryption information using the first encryption information when data to be transmitted is generated, and the second encryption information and the third encryption of the data. A method of transmitting a signal in a communication system, comprising: encrypting using information; and generating and transmitting a signal including the encrypted data and the first encrypted information. To do.

  Furthermore, the present invention is a method for transmitting an MBS (Multicast and Broadcast Service) stream in a communication system, and when MBS data to be transmitted is generated, the frame number and rollover counter (Rollover Counter :) of the communication system are generated. ROC) is used to generate an initial counter value, the initial counter value is incremented by 1 to generate n counter values, and the n counter values and MBS traffic key (MTK) are used. Generating n cipher blocks, fragmenting the MBS data into n plain texts, and performing an exclusive OR (XOR) operation on the n plain texts and the cipher blocks. Generating an MBS stream, and one of the n MBS streams and the previous And having a step of generating and transmitting the n MBS payloads including ROC, respectively.

  The present invention enables stable encryption / decryption by changing an initialization counter value for encryption / decryption even in a time interval using the same MTK. In addition, the present invention newly proposes an ROC corresponding to additional data to be transmitted for encryption / decryption, thereby reducing a decrease in data transmission capacity due to additional data transmission and increasing an overall data transmission capacity. There is an effect to make.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted for the purpose of simplifying the gist of the present invention.

  The present invention proposes an apparatus and method for ciphering / deciphering a signal in a communication system. This signal encryption / decryption device and method will be described by taking an IEEE (Institute of Electrical and Electronics Engineers) 802.16 communication system corresponding to a broadband wireless access (BWA) communication system as an example. The signal encryption / decryption device and method proposed by the present invention can be applied not only to the IEEE 802.16 communication system but also to other communication systems.

FIG. 3 is a block diagram illustrating a structure of a signal transmission device of the IEEE 802.16 communication system according to the embodiment of the present invention.
Referring to FIG. 3, the signal transmission device includes an AES-CTR encryption device used in AES (Advanced Encryption Standard) -CTR (Counter Mode) mode and an MBS (Multicast and Broadcast Service) payload generator 450. . The AES-CTR encryption apparatus includes an initial counter value generator 300 and an AES-CTR encoder 400. Since the structure of the AES-CTR encryptor 400 will be described later with reference to FIG. 4, a detailed description thereof will be omitted here.

  Research on the MBS of the IEEE 802.16 communication system is actively underway. Since MBS data requires encryption and decryption between a transmitter (eg, a base station (BS)) and a receiver (eg, a subscriber terminal (SS)) to provide the MBS, the MBS AES-CTR mode and encryption / decryption method are defined. The base station must send information for decryption to the SS so that the SS can decrypt the encrypted MBS data. In the IEEE 802.16 communication system, data used for generating an initial counter value as information for decoding must be included in the MBS payload and transmitted. The present invention proposes ROC (Rollover Counter) as data used to generate an initial counter value. Here, ROC is a value that increases every time the frame number used in the physical (PHY) layer of the IEEE 802.16 communication system increases. For example, the ROC is expressed by 8 bits. In the IEEE 802.16 communication system, the frame number is expressed by 24 bits.

  Therefore, in the present invention, 32 bits are generated using an 8-bit ROC and a 24-bit frame number, and the 32-bit initialization counter value is generated by repeating the 32 bits for a preset number of times, for example, 4 times. To do. As a result, according to the present invention, since there is no collision between the initial counter values due to the change of the frame number or the ROC in the time interval in which the same MBS Traffic Key (MBK) is used, there is reliability. Encryption and decryption are possible. That is, if the MTK refresh cycle is set longer than the cycle in which the ROC is repeated, the initial counter value is not reused, so that reliable encryption and decryption are possible.

  Referring to FIG. 3, the initial counter value generator 300 increases the ROC whenever the frame number of the PHY layer of the IEEE 802.16 communication system increases. The initial counter value generator 300 concatenates a 24-bit frame number and an 8-bit ROC to generate 32 bits, and repeats 4 times to generate a 128-bit initial counter value. Output to CTR encryptor 400 The initial counter value generator 300 outputs the ROC to the MBS payload generator 450.

  When MBS data to be transmitted is generated, the MBS data to be transmitted, the MTK, and the initial counter value are input to the AES-CTR encryptor 400. The AES-CTR encryptor 400 receives the MBS data, the MTK, and the initial counter value, encrypts the MBS data, generates an MBS stream, and outputs the MBS stream to the MBS payload generator 450. The MBS payload generator 450 generates an MBS payload including the MBS stream output from the AES-CTR encryptor 400 and the ROC output from the initial counter value generator 300. Also, the structure of the transmitter for transmitting the MBS payload is not shown in FIG. The MBS payload is transmitted to the corresponding SS through the transmitter.

FIG. 4 illustrates an MBS payload format according to an embodiment of the present invention.
Referring to FIG. 4, the MBS payload includes a comprehensive medium access control (MAC) header (GMH) field 411, an ROC field 413, an MBS stream field 415, and a CRC (Cyclic Redundancy Check) field 417. Including.

  The GMH field 411 includes a GMH corresponding to a MAC header having a predetermined length. The ROC field 413 includes the ROC used to generate the initial counter value of the counter in AES-CTR mode. The MBS stream field 415 includes an MBS stream. The CRC field 417 includes a CRC for confirming the occurrence of an error in the MBS payload. Here, the MBS stream included in the MBS stream field 415 is generated from the encrypted MBS data. The ROC size is 8 bits as described above. Therefore, in a general IEEE 802.16 communication system, the size is smaller than the 32-bit nonce used to generate the initial counter value, and a gain is obtained from the viewpoint of data transmission.

FIG. 5 is a block diagram showing the structure of the AES-CTR encryptor 400 of FIG.
Referring to FIG. 5, the AES-CTR encryptor 400 includes a counter 412, n cipher block generators, that is, first to n-th cipher block generators 413-1 to 413-n, and n cipher block generators. It includes exclusive OR (XOR) calculators, that is, first to nth XOR calculators 415-1 to 415-n.

  When MBS data to be transmitted is generated, the MBS data to be transmitted, an initial counter value, and an MBS traffic key (hereinafter referred to as “MTK”) are input to the AES-CTR encryptor 400. Here, the MBS data is fragmented into n plain texts, that is, first to nth plain texts. Each of the n plain texts is input to the corresponding XOR operator. That is, the first plain text is input to the first XOR operator 415-1, and similarly, the nth plain text is input to the nth XOR operator 415-n. The MTK is input to the first to nth cipher block generators 413-1 to 413-n.

  The counter 412 receives the initial counter value and increments it by n times to generate n counter values. The counter 412 outputs each of the n counter values to the corresponding cipher block generator. That is, the counter 412 outputs the first counter value generated by incrementing the initial counter value by 1 to the first cipher block generator 413-1. The counter 412 outputs the second counter value generated by incrementing the initial counter value by 2 to the second cipher block generator 413-2. In this manner, the counter 412 outputs the nth counter value generated by increasing the initial counter value by n to the nth cipher block generator 413-n.

  Each of the n cipher block generators receives the MTK and the counter value output from the counter 412 to generate a cipher block, and outputs the cipher block to the corresponding XOR operator. The first cipher block generator 413-1 generates the first cipher block using the first counter value output from the counter 412 and the MTK, and then sends the first cipher block to the first XOR operator 415-1. Output a cipher block. In this way, the nth cipher block generator 413-n generates the nth cipher block using the nth counter value output from the counter 412 and the MTK, and the nth XOR operator 415-n. This cipher block is output to

  Each of the n XOR operators receives the encryption block output from the corresponding encryption block generator and the corresponding plain text, performs an XOR operation, and outputs an MBS stream. That is, the first XOR operator 415-1 receives the first cipher block and the first plain text output from the first cipher block generator 413-1, and performs the XOR operation. An MBS stream is generated and output. As described above, the nth XOR operator 415-n receives the nth cipher block and the nth plain text output from the nth cipher block generator 413-n, and performs an XOR operation. The nth MBS stream is generated and output to the MBS payload generator 450.

FIG. 6 is a flowchart illustrating an AES-CTR encryption process of the IEEE 802.16 communication system according to an embodiment of the present invention.
Referring to FIG. 6, in step S611, the AES-CTR encryption apparatus generates n initial counter values using the frame number and the ROC when MBS data to be transmitted is input. In step S613, the AES-CTR encryption apparatus fragments the MBS data to generate n plain texts. In step S615, the AES-CTR encryption apparatus generates n cipher blocks using n initial counter values and MTK. In step S617, the AES-CTR encryption apparatus generates n MBS streams by performing an XOR operation on each of n plaintexts and n cipher blocks. Then, the above process ends.

  Although specific embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications can be made without departing from the scope of the present invention. That would be true. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined based on the scope of claims and the equivalents to the scope of claims.

1 is a diagram illustrating an MBS payload format used in a general IEEE 802.16 communication system. FIG. 1 is a block configuration diagram showing a configuration of an AES-CTR encryption apparatus used in an AES-CTR mode of a general IEEE 802.16 communication system. It is a block block diagram which shows the structure of the signal transmitter of the IEEE802.16 communication system by embodiment of this invention. FIG. 4 is a diagram illustrating an MBS payload format according to an embodiment of the present invention. FIG. 4 is a block configuration diagram showing a configuration of an AES-CTR encryptor 400 in FIG. 3. 5 is a flowchart illustrating AES-CTR encryption processing of the IEEE 802.16 communication system according to an embodiment of the present invention.

Explanation of symbols

300 Initial counter value generator 400 AES-CTR encryptor 450 MBS payload generator

Claims (13)

A signal transmission method in a communication system, comprising:
Generating an initial counter value for a multicast and broadcast service (MBS) data to be transmitted using a frame number and a rollover counter (ROC) of the communication system;
Encrypting the MBS data using the initial counter value and an MBS Traffic Key (MTS);
A signal transmission method for a communication system, comprising: generating and transmitting a signal including only the ROC and the encrypted MBS data among the ROC, the initial counter value, and the MTS . 2. The signal transmission method of the communication system according to claim 1 , wherein the ROC is increased by increasing the frame number . Generating the initial counter value comprises :
3. The communication system according to claim 2 , further comprising the step of concatenating the frame number and the ROC and generating the initial counter value by repeating the concatenation result a predetermined number of times. With signal transmission method. A signal transmission device in a communication system,
For a multicast and broadcast service (hereinafter referred to as “MBS”) data to be transmitted, an initial counter value is generated using a frame number and a rollover counter (ROC) of the communication system. An initial counter value generator;
An encryptor that encrypts the MBS data using an initial counter value and an MBS Traffic Key (MTS);
Of the ROC, the initial counter value, and the MTS, only the ROC
A signal generator for generating and transmitting a signal including the encrypted MBS data . The apparatus according to claim 4 , further comprising a transmitter that transmits the generated signal . The apparatus according to claim 4 , wherein the ROC is increased by increasing the frame number . The initial counter value generator according to claim 6, wherein the frame number and connects the rollover counter, and generating the initial counter value by repeating number of times is preset the consolidated results The device described. A method for transmitting an MBS (Multicast and Broadcast Service) stream in a communication system,
For the MBS data to be transmitted , generating an initial counter value using a frame number and a rollover counter (ROC) of the communication system;
Increasing the initial counter value by 1 to generate n counter values;
Generating n cipher blocks using the n counter values and an MBS traffic key (MTS);
Fragmenting the MBS data into n plain texts;
Generating an MBS stream by performing an exclusive OR (XOR) operation on the n plaintexts and the cipher block;
Of the ROC, the initial counter value, and the MTS, only the ROC
And generating and transmitting n MBS payloads including any one MBS stream among the n MBS streams . The method of claim 8, wherein the ROC is increased by increasing the frame number. Generating the initial counter value comprises:
The method according to claim 9 , further comprising the step of concatenating the frame number and the rollover counter and generating the initial counter value by repeating the concatenation result a predetermined number of times. An apparatus for transmitting an MBS (Multicast and Broadcast Service) stream in a communication system,
An initial counter value generator for generating an initial counter value using a frame number and a rollover counter (ROC) of the communication system;
For MBS data to be transmitted, a counter that increments the initial counter value by 1 to generate n counter values;
N cipher block generators that generate n cipher blocks using the n counter values and an MBS traffic key (MTS);
N XOR operators for performing an exclusive OR (XOR) operation on the n plaintexts generated by fragmenting the MBS data and the cipher block, and generating an MBS stream;
Of the ROC, the initial counter value, and the MTS, only the ROC
An MBS payload generator that generates n MBS payloads including any one MBS stream among the n MBS streams;
A transmitter for transmitting the n MBS payloads . The apparatus of claim 11, wherein the ROC is increased by increasing the frame number. The initial counter value generator, said frame number and connects the rollover counter, claim 11, characterized in that generating the initial counter value by repeating number of times is preset the consolidated results The device described.

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